The invention has been devised primarily in the context of light curing guns for dental filling materials. An example of a gun of this type is disclosed in U.S. Pat. No. 5,803,729 (Tsimerman). In a typical light curing gun, light from a halogen bulb is reflected into a light guide, by which the light is directed onto the dental filling material to be cured. Since the light guide necessarily enters the mouth of the patient, it should be sterile. If the same light guide is used repeatedly, it should be sterilized or replaced between patients. As disclosed in the Tsimerman patent, the light guide is simply push-fitted into a sleeve that provides a receptacle in the nose cone of the gun. Accordingly, it is quite a simple matter to change the light guide.
Traditionally, fibre optic light guides have been used. Performance of the curing light is significantly affected by the degree of transmission of light through a fibre optic light guide. Sterilization of these light guides results in decreased light transmission. In addition, cleaning and maintenance of fibre optic light guides is time consuming and costly.
Plastic disposable light guides were introduced several years ago. Re-use of non-sterilized light guides, which might even occur accidentally, would be hazardous to both the patient and to the dentist in view of the strict infection control guidelines of recent years. However, plastic light guides do not respond well to sterilization processes that employ heat. Lengthy immersion in cold sterilizing solutions causes cracking and yellowing of the plastic.
Similar considerations apply in relation to other medical devices that have replaceable patient-contact elements. Examples are electric toothbrushes where the toothbrush head typically is replaceable and dental irrigation devices having water nozzles. Sterility may not be as critical in these cases in the sense that there would normally be only a single user for one brush head. Nevertheless, toothbrush heads and nozzles do degrade with time and should periodically be replaced. Some types of medical syringe have dispensing tips that require replacement from time to time.
An object of the present invention is to provide means for at least indicating to the user of the device that the patient contact element should be replaced.